The present invention relates to a razor knife. More particularly this invention concerns such a knife with a hollow handle holding a slide displaceable between a use position with the blade projecting from the handle and a storage position with the blade retracted into the handle.
A standard utility knife as described in U.S. Pat. No. 4,835,865 of H. Knoop has a hollow handle provided with a blade-carrying slide displaceable between advanced and retracted positions. A return spring urges the slide back into the retracted position. The blade is held on pins projecting transversely from the slide and a retaining element hinged on the slide normally fits with the pins over the blade to hold it in place. The knife body has a main part carrying the slide and another part that can be removed to expose the retaining element and allow it to be swung out for removal and replacement of the blade. Such a knife is handy, but is normally set up for only one type of blade due to the type of holder, that is it can use standard trapezoidal disposable blades or square single-edge blades, but not both.
U.S. Pat. No. 3,708,881 of R. Bennett describes another slide-type razor knife where the slide is displaceable past the normal use position into a fully extended position in which the blade is fully exposed and can be lifted off the slide and into a full-rear position in which a blade magazine on the rear end of the slide is exposed. Thus to change blades the slide is first retracted fully to allow a fresh blade to be extracted from the supply in the magazine and then is advanced fully to allow the old blade to be removed and the new blade to be installed in place. This system has the disadvantage that, for instance, when cutting by drawing the knife back it is possible to accidentally shift into the fully extended position and have the blade fall off the slide.
It is therefore an object of the present invention to provide an improved hollow-handle razor knife.
Another object is the provision of such an improved hollow-handle razor knife which overcomes the above-given disadvantages, that is which can use different types of blades and that securely holds its blade regardless of the type of cutting.
A razor knife has according to the invention a hollow elongated housing having a front end slot and a slide seat part having a formation adapted to retain a blade and displaceable longitudinally in the housing through the slot between a longitudinally forwardly extended position with the blade retained on the formation lying mainly outside the housing and a longitudinally rearwardly retracted position with the blade retained on the formation wholly inside the housing. A retaining part is slidable on the seat part in a direction between a closed position overlying the blade and holding it in place on the seat part and an open position exposing the blade on the formation and allowing it to be removed therefrom. The parts have stop faces engageable with each other in the direction to prevent sliding of the retaining part on the seat part in the direction. One of the stop faces is displaceable transversely to the other to allow the parts to slide relative to each other in the direction. In the extended position of the seat part and open position of the retaining part the blade is exposed outside the housing and is not retained in place on the seat part by the retaining part.
Thus with this system the blade is changed by advancing the slide part while holding back the retaining part so that the slide part ends up projecting from the housing with the blade on it ready to be picked off and replaced. When the slide part is returned back into the housing it latches at the stop faces with the retaining part so that the two thereafter move together, holding the blade solidly as it is moved into and out of the housing.
According to the invention the direction of relative translatory movement of the slide parts is longitudinal so that the retaining part moves on the seat part in the same direction as the slide moves in the housing. More particularly one of the parts is formed with a longitudinally extending guide on which the other of the parts can slide. In the extended position of the seat part and closed position of the retaining part both parts project through the slot.
The retaining part according to the invention engages around the seat part. Specifically, the retaining part is of C-section and forms a pair of guide grooves and the seat part has edge ribs slidable in the grooves. Furthermore, each of the parts has a respective rearward extension. The extensions form the stop faces and one of the extensions is elastically transversely deformable to move the stop faces from a position longitudinally aligned with each other to a position longitudinally out of alignment with each other. Further cam formations on the extensions allow them to deflect as the retaining part is moved from the open to the closed position, whereupon the stop faces latch together and hold the parts in this position.
The one extension is formed with an actuating button that may be accessible through a port in the side of the housing. Alternately the housing has a pair of parts movable between a closed position encasing the slide and an open position exposing the slide so that the retaining part can only be unlatched and slid on the seat part when the housing is open.